(1) Field of the Invention
The present invention relates to electro-mechanical actuators and particularly to control systems which employ solenoids to impart movement to a controllable member. More specifically, this invention is directed to the exercise of control over a solenoid to enhance response time while minimizing power requirements. Accordingly, the general objects of the present invention are to provide novel and improved apparatus and methods of such character.
(2) Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well suited for use in time modulated controls of the type shown in U.S. Pat. No. 3,430,536. In such controls, in response to command and feedback signals and the output of a carrier frequency oscillator, a solenoid actuated control valve is operated in a pulse width modulated mode to deliver gas from a supply to a pneumatic actuator which, for example, positions a steering fin of a missile. Considering the missile control environment, it is necessary that the actuator respond quickly to command signals. However, because of space and weight limitations, the power consumption of the control must be minimized. These constraints on weight and space are particularly demanding in the case of batteries which supply power to the solenoid actuators of the control system. The requirements of fast response and low power consumption area, to a large extent, conflicting. Thus, attempts to minimize response time by reducing solenoid impedance are met by increased power consumption. Thus, the design of most prior art control systems employing solenoid actuators, particularly those systems intended for the demanding environment of a missile, has involved a compromise between fast response and low power consumption.